2021 Benjamin Franklin Medal in Physics presented to Henry C. Kapteyn, Ph.D. and Margaret M. Murnane, Ph.D

Henry Kapteyn and Margaret Murnane have pushed the boundaries of nonlinear optics to develop tabletop sources capable of producing short pulses of coherent, high-intensity, short-wavelength light. They use high harmonic generation, a unique quantum process that up-converts femtosecond lasers to very short wavelengths. This produces fully spatially and temporally coherent laser-like beams with controlled polarization throughout the extreme ultraviolet (EUV) and soft x-ray regions. In addition to leading the technology in developing these tabletop x-ray sources, Kapteyn and Murnane are leaders in using the sources to uncover new physics by conducting seminal experiments. These include: the study of attosecond processes in molecular physics in the gas phase; observation of light-induced spin transfer and fast relaxations following non-equilibrium phase transitions in magnetic systems; measurement of the dynamic electronic band structure of a correlated material driven into a new phase of matter by ultrafast laser excitation of electrons into metastable excited states; the study of electrons emitted from a metal surface due to the photoelectric effect (allowing the measurement of the difference in lifetimes of photoelectrons that are excited into unoccupied bands vs. free states); and uncovering new regimes of nanoscale heat transport relevant to nano and quantum devices, that are far more efficient than originally thought. Finally, Kapteyn and Murnane have pioneered the use of their tabletop x-ray sources for x-ray microscopes using coherent lensless imaging, demonstrating the first sub-wavelength full field imaging.